The data services hub, a system that supplies tax information and other data to websites run by the U.S. and 14 states to sell medical coverage, was unavailable after a malfunction at the data center that hosts it.

The center, operated by Verizon Communications Inc. unit Terremark, lost connectivity after workers tried to replace a failed networking component, Joanne Peters, U.S. Health and Human Services Department spokeswoman, wrote in an e-mail. Peters didn’t say when the failure happened or how long it would take to repair.

“Our engineers have been working with HHS and other technology companies to identify and address the root cause of the issue, said Jeffrey Nelson, a spokesman for New York-based Verizon. ‘‘It will be fixed as quickly as possible.’’ Nelson also declined to say when the breakdown occurred.

The Obama administration has been under fire since Oct. 1 for persistent problems with the computer systems assembled to help people compare and enroll in insurance plans under the Patient Protection and Affordable Care Act of 2010. President Barack Obama appointed his incoming chief economic adviser, Jeffrey Zients, to advise the health department on fixes to the system last week.

36 States

The federal site serves consumers in 36 states, including Texas and Florida. Websites run by most of the 14 states that chose to build their own have run better than the federal site, although all of the sites rely to some extent on the data services hub, which was built by a UnitedHealth Group Inc. unit, Quality Software Services Inc.

A notice on the federal website today warned visitors that the system was down.

‘‘We are experiencing technical difficulties and hope to have them resolved soon,’’ the notice said. ‘‘Please try again later. In a hurry? You might be able to apply faster at our Marketplace call center. Call 1-800-318-2596 to talk with one of our trained representatives about applying over the phone.’’

Zients said Oct. 25 that the federal website, called healthcare.gov, will function smoothly for most customers by the end of November and named QSSI as the system’s lead contractor, taking over a decision-making role former filled by officials at the U.S. Center for Medicare and Medicaid Services.

Matt Stearns, a spokesman for UnitedHealth, didn’t immediately respond to an e-mail asking about the failure.

Error Messages

Since opening Oct. 1, the federal exchange has been plagued by delays, error messages and hang-ups that have prevented many customers from completing applications. Zients’s statement that there will be a monthlong wait to repair the federal exchange set off new calls for the president to ease a key deadline for consumers to sign up.

Jeanne Shaheen, a New Hampshire Democrat who voted for the health law in 2010, is among 10 Democratic U.S. senators who wrote the administration to ask that the six-month enrollment period be lengthened. The call for the delay is linked to provisions in the law that requires all health plans to be compliant with provisions that include increase preventative care by January 2014.

If the website remains troubled until the beginning of December, it would cut the time given to consumers to change their health coverage to just a month. Insurers this month began sending out notices that they are canceling current plans, forcing consumers to sign up for new plans that are compliant with the law’s requirements either through the exchange or, in some states, independently with insurers.

Connecticut Exchange

Connecticut’s independent state exchange, known as Access Health CT, notified consumers in the early evening that their site would be partially disabled.

‘‘Customers will not be able to access Remote Identity Proofing, Social Security Administration or Advanced Premium Tax Credits also referred to as subsidies,” wrote Kathleen Tallarita, a spokeswoman for the state site, in a statement today. “As a result, consumers will not be able to complete the sign up process for Medicaid or Advanced Premium Tax Credit determinations.”

Connecticut consumers can continue to create accounts as well as shop anonymously for pricing comparisons, Tallarita said.

Computer servers hosting a key piece of Obamacare's insurance enrollment program failed today, leaving federal and independent state exchanges unable to provide most services.The data services hub, a system that supplies tax information and other data to websites run by the...